code: def _equal_var_ttest_denom(v1, n1, v2, n2):
      df = n1 + n2 - 2.0
      svar = ((n1 - 1) * v1 + (n2 - 1) * v2) / df
      denom = da.sqrt(svar * (1.0 / n1 + 1.0 / n2))  # XXX: np -> da
      return df, denom
  
imports: from __future__ import annotations
  import math
  from collections import namedtuple
  import numpy
  import dask.array
  from dask import delayed
  from dask.array.ufunc import wrap_elemwise
  from dask.utils import derived_from
  from scipy import special
  from scipy.stats import distributions
label_desc: Use image node_id 13 for calling a global function with example usage: _equal_var_ttest_denom(v1, n1, v2, n2) and returns: df,  denom